Security mechanisms for wireless sensor networks (WSN) face a great challenge due to the restriction of their small sizes and limited energy. Hence, many protocols for WSN are not designed with the consideration of security. Chaotic cryptosystems have the advantages of high security and little cost of time and space, so this paper proposes a secure cluster routing protocol based on chaotic encryption as well as a conventional symmetric encryption scheme. First, a principal-subordinate chaotic function called N-Logistic-tent is proposed. Data range is thus enlarged as compared to the basic Logistic map and the security is enhanced. In addition, the computation is easier, which does not take much resource. Then, a secure protocol is designed based on it. Most of communication data are encrypted by chaotic keys except the initialization by the base station. Analysis shows that the security of the protocol is improved with a low cost, and it has a balance between resource and security.
Irreversible behavior of the ground or a rock mass encompasses both the transition of the ground over a peak strength and further development of the nonreversible movement and deformation. The irreversible ground movement is traditionally considered as the transition to chaos. However the moving ground passes through itself the energy of ground pressure, thermal energy, and exchanges by substances with surrounding rock mass. According to thermodynamics of irreversible processes, such a non-equilibrium ground behavior may create dissipative structures that are the embodiment of self-organization. The paper describes the results of the structures investigation, which have been unveiled with incremental fields of the irreversible ground movement during a landslide development and underground roadway maintenance. These structures were evolving from close interaction of the separate blocks or fragments of the ground and distant cooperation of the short-lived clusters that were periodically rearranging in time and space as the irreversible ground movement started and progressed. Extant techniques restrain basically one prevalent component of the irreversible ground movement. The other two collateral transversal components were usually ignored. However, blocking of these transverse components can prevent the development of a dangerous irreversible movement of the ground and a rock mass.
The use of livestock guarding dogs (LGDs) has been widely advocated as a responsible tool for reducing livestock predation and conserving wildlife. However, their hidden ecological costs have rarely been investigated. We analysed scats (n = 183) from six LGDs and visited Global Positioning System (GPS) location clusters (n = 352) from nine GPS-collared LGDs to reconstruct their diet and assess impacts on wildlife and livestock in Namaqualand, South Africa. Wild mammals, including 10 native species, and small-livestock were the main secondary foods (i.e. besides dog food pellets). A total of 90% of scats and one third of GPS clusters investigated had associated animal remains. When accompanied by a human attendant, fewer LGD scats contained animal matter (39.9%; of which 32.3% wild mammals and 4.6% livestock), in contrast to scats of LGDs on their own (93.2%; 14.4% wild mammals, 75.4% livestock). Similarly, few clusters of accompanied LGDs included animal remains (5.7%; of which 43.8% wild mammals and 31.3% livestock), whereas unaccompanied dogs clustered frequently at carcasses (92.4%; 16% wild mammals, 74% livestock). While sample sizes were relatively small and some dogs might have scavenged, we emphasize the importance of rigorous training and intensive monitoring of LGDs to correct unwanted predation behaviour and to maximize their ecological and protective benefits.